Name: This Diagram of Earth Is a Lie
Uploaded: 2020-03-30T03:38:55.000Z
Duration: 5 min 23 s
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When you learned about the Earth's interior

in elementary school, you were probably shown

You had the thin crust, the thicker section of the mantle,

we've known for a long time that that diagram

gigantic blobs the size of continents in it.

And we're now learning that those irregularities

may actually be fundamentally important to

To do this kind of work, scientists use seismometers:

instruments about the size of a gallon of

They're most famous for studying earthquakes,

but they can also be used to examine other

seismometer data can also help you figure

For instance, when a big earthquake happens,

it releases energy that radiates out from

in all directions, but they don't go in a

and they don't all travel the same speed.

Instead, their speed depends on the temperature

and density of the rock they're moving through.

For example, hot, molten rock slows down the

seismic waves a lot, while cold, dense material

So by using seismometers to monitor the arrival

times of these waves at different locations,

scientists can figure out the density of rock

layers inside the Earth and what they're made of.

This kind of work is called seismic tomography,

and it's the main way we know what the inside

It's also how we discovered that the mantle

The mantle is a thick layer of solid-ish rock,

the Pacific Ocean, and one beneath Africa

These two arm-like protrusions were discovered

the core-mantle boundary and extend up toward

Scientists can see them in tomographic images because they're

Then, when the waves exit the blobs, they change speed again.

This weird behavior likely has to do with what the blobs are made of.

Scientists haven't figured out their composition

for sure, but an experiment from 2017 suggested

And they might have formed when iron-rich rock

from the mantle reacted with seawater under

enormous pressures and high temperatures.

Seawater sometimes gets into the mantle as

tectonic plates move underneath each other.

According to preliminary studies, a composition

like this would give us the kind of seismic

Of course, scientists want to know more than

just what these things are made of. They also

want to know how they fit into the larger scheme of things on Earth.

There are a bunch of questions to answer here,

but at least right now, these blobs seem to

Like, nearly all the hotspots on Earth — that

is, all the volcanic centers not associated

Hawai'i is pretty much centered over the one below the Pacific Ocean,